Alzheimer's disease (AD) is a dementia that affects 4 million elderly individuals in the USA and this number is projected to quadruple by 2050. This neurodegenerative disorder strikes 4% of individuals at 65 years of age and as many as 40% of those at age 85 at a cost of over $100 billion annually. There is an urgent need for effective therapeutic interventions that may prevent, delay the age of onset or relent the course of this dementia. Transgenic (Tg) mice expressing human AD genes such as amyloid- precursor protein (APP), presenilin (PS), the microtubule protein tau, -amyloid cleaving enzyme-1 (BACE-1), and a-synuclein have provided tools to investigate both the pathogenesis and the efficacy of treatments for these neuropathological disorders. Our goal, in Specific Aim 1, is to better understand the strengths and limitations of several Tg mice models by establishing the degree of biochemical similarities and differences between these paradigms and human AD subjects. In Specific Aim 2, soluble and deposited A remaining after anti- A active and passive immunizations of AD patients will be quantitatively and qualitatively assessed in gray and white matter and cerebral vasculature to evaluate the effects of immunization on A dynamics and its clinical impact on the course of AD. In Specific Aim 3, the APP and A peptides retained in the brain microsomal, mitochondrial and lipid raft brain fractions in AD and non-demented controls will be determined to better understand the role of neuronal and glial participation in the pathophysiology of AD. To achieve these three objectives physicochemical techniques involving the use of density and affinity gradients, chaotropic agents, multiple chromatographic separations, amino acid analysis, peptide sequencing, mass spectrometry, bioinformatics data bases, immunoassays and Western blotting will be implemented. The proposed studies will: 1) aid in the accurate interpretation of Tg mouse experimental responses, 2) help to elucidate at the molecular level the direct and indirect effects of anti- A immunization and 3) discover the pathological consequences, beyond soluble A and deposited amyloid, of membrane-retained APP/ A peptides. A more complete understanding of AD molecular phenotypes and their clinical responses will aid in the discovery and application of efficacious treatments that will prevent AD or enhance the quality of life of AD patients.